To define more clearly and to treat those disorders affecting the neuromuscular apparatus which present primarily with episodic weakness or paralysis or are characterized by a significant amount of myotonia. Attention is directed toward those conditions in which evidence suggests that the main site of intermittent dysfunction is somewhere within the following portions of the muscle fiber: plasmalemma, T-system, sarcoplasmic reticulum, myofibrillar complex (i.e., the total excitation-contraction coupling mechanism). With respect to periodic paralysis syndromes, studies are done with agents which are transiently either therapeutic or provocative, with a view to obtaining more information regarding abnormalities of pertinent metabolic pathways and methods of treatment. The various myotonia disorders are studied with respect to more clearly defining the molecular abnormalities, seeking the underlying pathogeneses and treatment thereof, and finding better ways of symptomatically treating their myotonia. Induced animal-models of myotonia are also used for these purposes. Tissue culture of the human abnormal muscle is used for purposes of reincarnating disease in culture and then its treatment, and for induction of models of disease by chemical agents, which are also used to induce models in cultured human or animal muscle.